Project description:The regulation of proteostasis is fundamental for maintenance of muscle mass and function. Activation of the TGF-β pathway drives wasting and premature aging by favoring the proteasomal degradation of structural muscle proteins. Yet, how this critical post-translational mechanism is kept in check to preserve muscle health remains unclear. Here, we reveal the molecular link between the post-transcriptional regulation of m6A-modified mRNA and the modulation of SMAD-dependent TGF-β signaling. We show that the m6A-binding protein YTHDF2 is essential to determining postnatal muscle size. Indeed, muscle-specific genetic deletion of YTHDF2 impairs skeletal muscle growth and abrogates the response to hypertrophic stimuli. We report that YTHDF2 controls the mRNA stability of the ubiquitin ligase ASB2 with consequences on anti-growth gene program activation through SMAD3. Our study identifies a post-transcriptional to post-translational mechanism for the coordination of gene expression in muscle.
Project description:Muscle atrophy F-box (MAFbx) is an E3 ubiquitin ligase which plays a critical role in mediating skeletal muscle atrophy. We investigated the effect of MAFbx KO in cardiac hypertrophy in response to pressure overload. A DNA microarray analysis was conducted using total RNA prepared from wild type and MAFbx KO mouse hearts subject to transverse aortic constriction (TAC). Results provide insight into the molecular mechanism to mediate the effect of MAFbx upon pathological hypertrophy. We applied TAC to wild type and MAFbx KO mice, and extracted total RNA one week after the surgery. The gene expression profiles were examined by Affymetrix Mouse Gene ST Array.
Project description:Skeletal muscle is dynamically controlled by the balance of protein synthesis and degradation. Here we discover an unexpected function for the transcriptional repressor B cell lymphoma 6 (BCL6) in muscle proteostasis and strength in mice. Skeletal muscle-specific Bcl6 ablation in utero or in adult mice results in over 30% decreased muscle mass and force production due to reduced protein synthesis and increased autophagy, while it promotes a shift to a slower myosin heavy chain fibre profile. Ribosome profiling reveals reduced overall translation efficiency in Bcl6-ablated muscles. Mechanistically, tandem chromatin immunoprecipitation, transcriptomic and translational analyses identify direct BCL6 repression of eukaryotic translation initiation factor 4E-binding protein 1 (Eif4ebp1) and activation of insulin-like growth factor 1 (Igf1) and androgen receptor (Ar). Together, these results uncover a bifunctional role for BCL6 in the transcriptional and translational control of muscle proteostasis.
Project description:The expression of the small molecular weight heat shock protein (Hsp) H11 kinase/Hsp22 (Hsp22) is restricted to a limited number of tissues, including the heart and skeletal muscle, both in rodents and in humans. We generated a mouse knockout (KO) model, and investigated the role of Hsp22 in regulating cardiac hypertrophy in response to pressure overload. We compared gene expression profiles between WT and KO mice in basal condition and three days pressure overload after transverse aortic constriction (TAC). These data illustrated a novel mechanism of Hsp22-related gene expression in response to cardiac stress. We used microarray to examine differential gene expression by Hsp22 deletion at baseline and 3-day pressure overload. Left ventricles from wild type and Hsp22 knockout mice were selected from basal condition (each, n=3) and TAC surgery (each, n=4).
Project description:In humans, cardiac hypertrophy is the principal risk factor for the development of overt heart failure and sudden cardiac death from lethal arrhythmias. Although aberrant reactivation of fetal² gene programs is intricately linked to maladaptive hypertrophy of postnatal cardiomyocytes, loss of cardiac function and heart failure, the transcription factors driving these gene programs remain ill defined. We report that the basic helix-loop-helix (bHLH) transcription factor dHAND/Hand2 is re-expressed in the mammalian postnatal myocardium in response to stress signaling. Interestingly, mutant mice overexpressing Hand2 in otherwise healthy ventricular myocytes developed a phenotype of pathological hypertrophy. In contrast, conditional gene-targeted Hand2 mice demonstrated a marked resistance to pressure overload-induced hypertrophy, fibrosis, ventricular dysfunction and induction of a fetal gene program. These data suggest a critical role for the Hand2 transcription factor during hypertrophic remodeling and heart failure. To gain more mechanistically insight in the processes underlying heart failure, we here identified Hand2 target genes by microarray gene expression profiling. RNA samples were collected 4 weeks after sham or TAC surgery (to induce pressure overload) of both tamoxifen-treated Hand2f/f (WT) and MCM-Hand2f/f (KO) mice.
Project description:Reduced insulin/IGF signaling increases lifespan in many animals. To understand how insulin/IGF mediates lifespan in Drosophila, we performed chromatin immunoprecipitation-sequencing analysis with the insulin/IGF regulated transcription factor dFOXO in long-lived insulin/IGF signaling genotypes. Dawdle, an Activin ligand, is bound and repressed by dFOXO when reduced insulin/IGF extends lifespan. Reduced Activin signaling improves performance and protein homeostasis in muscles of aged flies. Activin signaling through the Smad binding element inhibits the transcription of Autophagy-specific gene 8a (Atg8a) within muscle, a factor controlling the rate of autophagy. Expression of Atg8a within muscle is sufficient to increase lifespan. These data reveal how insulin signaling can regulate aging through control of Activin signaling that in turn controls autophagy, representing a potentially conserved molecular basis for longevity assurance. While reduced Activin within muscle autonomously retards functional aging of this tissue, these effects in muscle also reduce secretion of insulin-like peptides at a distance from the brain. Reduced insulin secretion from the brain may subsequently reinforce longevity assurance through decreased systemic insulin/IGF signaling.
Project description:The early life environment significantly affects the development of age-related skeletal muscle disorders. However, the long-term effects of lactational protein restriction on skeletal muscle are still poorly defined. Our study revealed that male mice nursed by dams fed a low-protein diet during lactation exhibited skeletal muscle growth restriction. This was associated with a dysregulation in the expression levels of genes related to the ribosome, mitochondria and skeletal muscle development. We reported that lifelong protein restriction accelerated loss of type-IIa muscle fibres and reduced muscle fibre size by impairing mitochondrial homeostasis and proteostasis at 18 months of age. However, feeding a normal-protein diet following lactational protein restriction prevented accelerated fibre loss and fibre size reduction in later life. These findings provide novel insight into the mechanisms by which lactational protein restriction hinders skeletal muscle growth and includes evidence that lifelong dietary protein restriction accelerated skeletal muscle loss in later life.
Project description:Protein homeostasis (proteostasis) is a potential mechanism that contributes to cancer cell survival and drug resistance. Constitutively active androgen receptor (AR) variants confer anti-androgen resistance in advanced prostate cancer. However, the role of proteostasis involved in next generation anti-androgen resistance and the mechanisms of AR variant regulation are poorly defined. Here we show that the ubiquitin-proteasome-system (UPS) is suppressed in enzalutamide/abiraterone resistant prostate cancer. AR/AR-V7 proteostasis requires the interaction of E3 ubiquitin ligase STUB1 and HSP70 complex. STUB1 disassociates AR/AR-V7 from HSP70, leading to AR/AR-V7 ubiquitination and degradation. Inhibition of HSP70 significantly inhibits prostate tumor growth and improves enzalutamide/abiraterone treatments through AR/AR-V7 suppression. Clinically, HSP70 expression is upregulated and correlated with AR/AR-V7 levels in high Gleason score prostate tumors. Our results reveal a novel mechanism of anti-androgen resistance via UPS alteration which could be targeted through inhibition of HSP70 to reduce AR-V7 expression and overcome resistance to AR-targeted therapies.
Project description:Global gene expression patterns were determined from microarray results from sham surgery or following 1 week of plantaris muscle hypertrophy induced by synergist ablation in young adult Pax7-DTA mice (4 months). Vehicle treated mice have their full complement of satellite cells; tamoxifen treated mice have had their satellite cells genetically depleted through Cre-loxP technology After sham surgery or 1 week of overload, Affymetrix chips (mouse430_2.0) were used with 1 µg of total RNA derived from a pooled sample of the right and left plantaris muscles from 11 animals.
Project description:To investigate the role of the circadian clock gene Bmal1 in skeletal muscle, we compared the circadian transcriptomes of fast tibialis anterior (TA) and slow soleus (SOL) skeletal muscles from muscle-specific Bmal1 KO (mKO) and their control Cre- littermates (Ctrl). Keyword: Circadian Transcriptome, time course 72 samples were analyzed, comprised of 4 experimental groups (Ctrl SOL, mKO SOL, Ctrl TA, mKO TA), with 3 biological replicates for each time point sampled every 4 hours for 24 hours. SOL and TA muscles were collected from the same animals, as indicated by Source Animal ID data column